1. Field of the Invention
The present invention relates to an optical receiver used in optical communication and a method of manufacturing the optical receiver. More specifically, the present invention relates to an optical receiver in which parasitic inductance, etc. is reduced and which is suitable for high-speed response, and a method of manufacturing the optical receiver
2. Description of the Background Art
FIGS. 12(A) and 12(B) show a longitudinal sectional structure of a conventional optical receiver. FIG. 12(A) is a front sectional view, and FIG. 12(B) is a side sectional view taken along a section line B—B in FIG. 12(A). An optical receiver 100 shown in FIGS. 12(A) and 12(13) is generally called a CAN type package and is fabricated as follows. After fixing a submount 102 on a package 103, a photodiode (PD) 101 serving as a light receiving device is fixed to the submount 102 by soldering. A plurality of lead pins 104, which are inserted through the package 103, for supplying electrical power or discharging electrical signals are connected to the PD 101 or the submount 102 with wires 105, respectively. A cap 107 provided with a converging lens 106 at its top portion is placed so as to cover the submount 102 and the PD 101, and an optical fiber 108 is fixed in a position above the lens 106. Then, a cover is placed as indicated by the broken lines connecting the optical fiber 108 and the package 103 in FIG. 12, whereby the optical receiver 100 is completed (see, e.g., Japanese Unexamined Utility Model Application Publication No. 4-081107). In the optical receiver 100 thus constructed, the PD 101 receives light incident from the optical fiber 108 through the converging lens 106.
In using the optical receiver 100, it is usually required to amplify an electrical output from the PD 101. Therefore, as shown in FIG. 13, in the conventional optical receiver 100 the lead pins 104 are bent to be mounted on a board (circuit board) 109, and an amplifier 110 is disposed in a rear portion of the board 109 and connected to the optical receiver 100 by wires 105. More specifically, a wiring pattern 111 is formed on the board 109, the lead pins 104 of the optical receiver 100 are soldered to the wiring pattern 111, and the amplifier 110 is connected to the wiring pattern 111 by the wires 105. In other words, the lead pins 104 of the optical receiver 100 and the amplifier 110 are connected to each other through the wires 105 and the wiring pattern 111. Note that an electronic circuit component (not shown) is also mounted on the board 109 behind the amplifier 110.
In recent years, increasingly widespread use of optical communication systems has required optical receivers to be mass-produced at a lower cost in a shorter time. An increase in capacity of transmission is also demanded. High-speed and large-capacity transmission on the order of 1 Gbps, 2.5 Gbps or more has been required in comparison with a conventional level of 156 Mbps or 622 Mbps.
However, it has been difficult to apply the above-described conventional optical receiver to high speed response, since the conventional optical receiver has the drawback that the parasitic inductance, parasitic capacitance, etc. are increased because the optical receiving device and the amplifier, which are separately provided, are connected to each other through a wire and wiring pattern, with a considerable distance existing between the PD in the optical receiver and the amplifier on the board. In particular, the distance between the PD and the amplifier is increased because the lead pins are connected to the board in a bent shape. Such an increase of parasitic inductance and parasitic capacitance makes it difficult to apply the conventional optical receiver to high speed response.
Another problem is that because the optical receiver and the amplifier are separately provided, the board for mounting those components requires a large area. Further, after fabricating the optical receiver, the optical receiver is mounted on the board and connected to the amplifier. Hence, the number of manufacturing steps up to connecting the PD and the amplifier is increased and a relatively long manufacturing time is required.